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Discussion Starter · #1 ·
2005 Titan. When purchased it had a hitch and power break package but no relays. I had the dealer check it all out and they added the relays, one brown and two blue. All has been working. Found the break light on the passenger side was not working yesterday.

Checked the bulb – looks good – swapped to other side. Drivers works - passenger does not.

Measured current at hitch, good on both sides

Measured current at lights – funny current reading on passenger, .4 ? Thought bad wiring?? Older trailer. Rewired trailer. NO break light on passenger side.

Pulled wire off light assembly, measured current at wire – full 12 V. WHEN I CONNECT THE WIRE FROM THE LIGHT ASSEMBLY POWER DROPS TO .4 ???

Thinking it must be some type of short in the light assembly; I open it up but see no short or problem. Buy new light assembly – SAME ISSUE! READING THE WIRE FROM THE TRAILOR FULL 12V, CONNECT THE LIGHT AND CURRENT DROPS TO .4 v AND NO LIGHT???

Could this be some type of failure in the relay?
 

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If power is getting all the way to the back of the trailer, that would lead me to believe it's a light assembly issue. With no fuses popping than there should be no short through that length of wire. I know you said you installed a new light assembly, did you possibly gain a bad bulb with the new assembly? Otherwise I would pull the wiring back off the new assembly and double check the wiring there. Good luck! I always hate chasing wiring gremlins. If you have a new relay or can swap it with another one try that as well.
 

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Discussion Starter · #3 ·
I was going to try swapping the two blue relays but I do not know 1) if they are interchangable and 2) if they each control left and right seperatly. I'm assuming this is a good step but wanted confirmation before I try it.
 

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bad ground on that single light fiture.
 

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Discussion Starter · #6 ·
bad ground on that single light fiture.
I removed the light assembly from the trailer, have the power wire connected and then touch it to another ground spot on the trailer. Same issue, as soon as the circuit is complete, the power reading drops to .4. Same with both the new and old light assembly and testing on different ground spots.
 

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Swap the relays. Won't hurt anything. It's possible it's the relay, but I think it's unlikely.
 

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Set meter to measure resistance (ohms), disconnect wires to trailer light assemblies, measure resistance across terminals of light assemblies.

BTW: Power = watts. Voltage = volts. Power is not the same thing as voltage. Current = amps. Current is not the same thing as voltage. Power (watts) = V (volts) x I (current measured in amps). V (volts) = I (amps) x R (resistance measured in ohms).
 

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Discussion Starter · #9 ·
Swapped relays - problem followed the relay. Passenger now works. Drivers does not. Not going to wait for the dealer... NAPA $9...

Thanks for all in input !
 

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Where are the relays?

My trailer running lights work, but my driver side brake light and directional do not work on my 04 Titan. I have an 05 Titan also and all works well when connected to this truck.

I have tested at the receiver on the truck and the left blinker is dead. I've had intermittent problems before but it always seemed a big enough bump in the road would fix it.
 

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Relays are under the hood. Passengers side, close to the firewall. Look for a black box.
 

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My guess is that the relay is putting out a ghost voltage. You can read it on your meter but when you put it under load the voltage drops and doesn't do any work.
 
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